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Section 10
Use in 400Hz Multi 9
Miniature circuit
breakers
9
The greater part of Multi 9 circuit breakers are used on 400 Hz networks.
Short-circuit currents at 400 Hz generator terminals do not, in general, exceed the
nominal current by more than 4 times. Therefore, breaking capacity problems are very
rare.
Multi 9 circuit breakers
The C120 and NG125 circuit breakers cannot be used on 400 Hz network.
b
b
For the others :
No thermal derating
b
b
Increase of magnetic thresholds:
b
b
Coefficient 1.5 for DPN, DPN N and DPNa
v
v
Coefficient 1.48 for C60
v
v
Coefficient 1.40 for NC100
v
v
Residual current circuit breakers from the Multi 9 range can be used on 400 Hz
b
b
networks. It should be noted that the mA threshold varies depending on the
network’s frequency (see curves below).
Note:
In 400 Hz, the test circuit for residual current devices may present the risk of not
functioning when actioning the test button because of threshold variation.
According to international studies (IEC 60479-2), the human body is less sensitive to
a 400 Hz current that passes through the body; so well that, even though the residual
current device has had its frequency desensitised, these devices still ensure the
protection of persons. The method for choosing residual current devices in 400 Hz is
thus the same as that for 50 Hz.
RCCB
Operating residual current variation curves
Type
Rating (A)
Curve n°
Sensitivity (mA)
10
30
100
300
500
AC
25
2
1
-
1
1
25-40
-
1
1
1
1
63-80-100
-
2
1
1
1
A
16-25-40-63 -
3
-
2
2
A si, SiE
-
4
-
4
-
Selective
s
(AC, A)
-
-
-
2
2
Hz
250 350 400
1
2
3
4
0.5
1.5
10
50 60
Hz
ID
l n
90 150 250 350
1
2
2.5
400
1
2
3
4